Is Boris Johnson getting too big for his boots? That seems to be the perception in Downing Street and it is a sentiment clearly shared by many of David Cameron’s Cabinet colleagues. Boris, who has cemented his position as a leading rival to the Prime Minister, has just had his wings rudely clipped by Culture Secretary Maria Miller.

Asked in a written parliamentary question “what plans she has for the devolution of additional powers to the Mayor of London”, Mrs Miller delegated the reply to her junior minister, Hugh Robertson. This was a terrible snub in itself and Boris won’t like the response. “My department has no immediate plans to devolve additional powers specifically to the Mayor of London,” the minister said.

Instead of expanding Boris’s empire, Robertson said, power should be devolved “to the lowest appropriate level — down to councils, to neighbourhoods, to community groups and to individuals”.

Business minister Michael Fallon was asked the same question and came back yesterday with a similarly curt brush-off. “The department has no plans to devolve any additional powers to the Mayor of London,” he responded.

So it looks as if Boris’s colleagues are intent on quashing his imperial ambitions. Perhaps Boris will remember the snub when he sweeps back into Parliament.